Twofold Axis Research Articles

N-Tosyl-L-proline benzene hemisolvate: a rare example of a hydrogen-bonded carboxylic acid dimer with symmetrically disordered H atoms.

The carboxylic acid group is an example of a functional group which possess a good hydrogen-bond donor (-OH) and acceptor (C=O). For this reason, carboxylic acids have a tendency to self-assembly by the formation of hydrogen bonds between the donor and acceptor sites. We present here the crystal structure of N-tosyl-L-proline (TPOH) benzene hemisolvate {systematic name: (2S)-1-[(4-methylbenzene)sulfonyl]pyrrolidine-2-carboxylic acid benzene hemisolvate}, C12H15NO4S·0.5C6H6, (I), in which a cyclic R22(8) hydrogen-bonded carboxylic acid dimer with a strong O-(1/2H)...(1/2H)-O hydrogen bond is observed. The compound was characterized by single-crystal X-ray diffraction and NMR spectroscopy, and crystallizes in the space group I2 with half a benzene molecule and one TPOH molecule in the asymmetric unit. The H atom of the carboxyl OH group is disordered over a twofold axis. An analysis of the intermolecular interactions using the noncovalent interaction (NCI) index showed that the TPOH molecules form dimers due to the strong O-(1/2H)...(1/2H)-O hydrogen bond, while the packing of the benzene solvent molecules is governed by weak dispersive interactions. A search of the Cambridge Structural Database revealed that the disordered dimeric motif observed in (I) was found previously only in six crystal structures.

Capsid Structure of a Freshwater Cyanophage Siphoviridae Mic1

Cyanobacteria are the most abundant photosynthetic microorganisms, the global distribution of which is mainly regulated by the corresponding cyanophages. A systematic screening of water samples in the Lake Chaohu enabled us to isolate a freshwater siphocyanophage that infects Microcystis wesenbergii, thus termed Mic1. Using cryoelectron microscopy, we solved the 3.5-Å structure of Mic1 capsid. The major capsid protein gp40 of an HK97-like fold forms two types of capsomers, hexons and pentons. The capsomers interact with each other via the interweaved N-terminal arms of gp40 in addition to a tail-in-mouth joint along the three-fold symmetric axis, resulting in the assembly of capsid in a mortise-and-tenon pattern. The novel-fold cement protein gp47 sticks at the two-fold symmetric axis and further fixes the capsid. These findings provide structural insights into the assembly of cyanophages, and set up a platform to explore the mechanism of specific interactions and co-evolution with cyanobacteria.

Cations Controlling the Chiral Assembly of Luminescent Atomically Precise Copper(I) Clusters.

Chiral assembly and asymmetric synthesis are critically important for the generation of chiral metal clusters with chiroptical activities. Here, a racemic mixture of [K(CH3 OH)2 (18-crown-6)]+ [Cu5 (St Bu)6 ]- (1⋅CH3 OH) in the chiral space group was prepared, in which the chiral red-emissive anionic [Cu5 (St Bu)6 ]- cluster was arranged along a twofold screw axis. Interestingly, the release of the coordinated CH3 OH of the cationic units turned the chiral 1⋅CH3 OH crystal into a mesomeric crystal [K(18-crown-6)]+ [Cu5 (St Bu)6 ]- (1), which has a centrosymmetric space group, by adding symmetry elements of glide and mirror planes through both disordered [Cu5 (St Bu)6 ]- units. The switchable chiral/achiral rearrangement of [Cu5 (St Bu)6 ]- clusters along with the capture/release of CH3 OH were concomitant with an intense increase/decrease in luminescence. We also used cationic chiral amino alcohols to induce the chiral assembly of a pair of enantiomers, [d/l-valinol(18-crown-6)]+ [Cu5 (St Bu)6 ]- (d/l-Cu5V ), which display impressive circularly polarized luminescence (CPL) in contrast to the CPL-silent racemic mixture of 1⋅CH3 OH and mesomeric 1.

Cations Controlling the Chiral Assembly of Luminescent Atomically Precise Copper(I) Clusters

AbstractChiral assembly and asymmetric synthesis are critically important for the generation of chiral metal clusters with chiroptical activities. Here, a racemic mixture of [K(CH3OH)2(18‐crown‐6)]+[Cu5(StBu)6]− (1⋅CH3OH) in the chiral space group was prepared, in which the chiral red‐emissive anionic [Cu5(StBu)6]− cluster was arranged along a twofold screw axis. Interestingly, the release of the coordinated CH3OH of the cationic units turned the chiral 1⋅CH3OH crystal into a mesomeric crystal [K(18‐crown‐6)]+[Cu5(StBu)6]− (1), which has a centrosymmetric space group, by adding symmetry elements of glide and mirror planes through both disordered [Cu5(StBu)6]− units. The switchable chiral/achiral rearrangement of [Cu5(StBu)6]− clusters along with the capture/release of CH3OH were concomitant with an intense increase/decrease in luminescence. We also used cationic chiral amino alcohols to induce the chiral assembly of a pair of enantiomers, [d/l‐valinol(18‐crown‐6)]+[Cu5(StBu)6]− (d/l‐Cu5V), which display impressive circularly polarized luminescence (CPL) in contrast to the CPL‐silent racemic mixture of 1⋅CH3OH and mesomeric 1.

(1Z,2Z)-1,2-Bis{2-[3,5-bis(trifluoromethyl)phenyl]hydrazinylidene}-1,2-bis(4-methoxyphenyl)ethane including an unknown solvate

The complete molecule of the title compound, C32H22F12N4O2, is generated by a crystallographic twofold axis aligned parallel to [010]. The F atoms of one of the CF3 groups are disordered over three orientations in a 0.6: 0.2: 0.2 ratio. In the crystal, molecules are linked by N—H...O hydrogen bonds, forming zigzag chains propagating along the a-axis direction. In addition, weak C—H...O and C—H...F bonds are observed. The contribution of the disordered solvent to the scattering was removed using the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9–18] of PLATON. The solvent contribution is not included in the reported molecular weight and density.

Crystal structure of catena-poly[[gold(I)-μ-cyanido-[di-aqua-bis-(2-phenyl-pyrazine)-iron(II)]-μ-cyanido] dicyanidogold(I)

In the title polymeric complex, {[Fe(CN)2(C10H8N2)2(H2O)2][Au(CN)2]} n , the FeII ion, which is located on a twofold rotation axis, has a slightly distorted FeN4O2 octa-hedral geometry. It is coordinated by two phenyl-pyrazine mol-ecules, two water mol-ecules and two di-cyano-aurate anions, the Au atom also being located on a second twofold rotation axis. In the crystal, the coordinated di-cyano-aurate anions bridge the FeII ions to form polymeric chains propagating along the b-axis direction. In the crystal, the chains are linked by Owater-H⋯Ndi-cyano-aurate anions hydrogen bonds and aurophillic inter-actions [Au⋯Au = 3.5661 (3) Å], forming layers parallel to the bc plane. The layers are linked by offset π-π stacking inter-actions [inter-centroid distance = 3.643 (3) Å], forming a supra-molecular metal-organic framework.

Crystal structures and Hirshfeld surface analysis of a series of 4-O-aryl-perfluoro-pyridines.

Five new crystal structures of perfluoro-pyridine substituted in the 4-position with phen-oxy, 4-bromo-phen-oxy, naphthalen-2-yl-oxy, 6-bromo-naphthalen-2-yl-oxy, and 4,4'-biphen-oxy are reported, viz. 2,3,5,6-tetra-fluoro-4-phen-oxy-pyridine, C11H5F4NO (I), 4-(4-bromo-phen-oxy)-2,3,5,6-tetra-fluoro-pyridine, C11H4BrF4NO (II), 2,3,5,6-tetra-fluoro-4-[(naphthalen-2-yl)-oxy]pyridine, C15H7F4NO (III), 4-[(6-bromo-naphthalen-2-yl)-oxy]-2,3,5,6-tetra-fluoropyridine, C15H6BrF4NO (IV), and 2,2'-bis-[(perfluoro-pyridin-4-yl)-oxy]-1,1'-biphenyl, C22H8F8N2O2 (V). The dihedral angles between the aromatic ring systems in I-IV are 78.74 (8), 56.35 (8), 74.30 (7), and 64.34 (19)°, respectively. The complete mol-ecule of V is generated by a crystallographic twofold axis: the dihedral angle between the pyridine ring and adjacent phenyl ring is 80.89 (5)° and the equivalent angle between the biphenyl rings is 27.30 (5)°. In each crystal, the packing is driven by C-H⋯F inter-actions, along with a variety of C-F⋯π, C-H⋯π, C-Br⋯N, C-H⋯N, and C-Br⋯π contacts. Hirshfeld surface analysis was conducted to aid in the visualization of these various influences on the packing.

5-Methyl-1,3-phenyl-ene bis-[5-(di-methyl-amino)-naphthalene-1-sulfonate]: crystal structure and DFT calculations.

The title compound, C31H30N2S2O6, possesses crystallographically imposed twofold symmetry with the two C atoms of the central benzene ring and the C atom of its methyl substituent lying on the twofold rotation axis. The two dansyl groups are twisted away from the plane of methyl-phenyl bridging unit in opposite directions. The three-dimensional arrangement in the crystal is mainly stabilized by weak hydrogen bonds between the sulfonyl oxygen atoms and the hydrogen atoms from the N-methyl groups. Stacking of the dansyl group is not observed. From the DFT calculations, the HOMO-LUMO energy gap was found to be 2.99 eV and indicates n→π* and π→π* transitions within the mol-ecule.

Heterologous expression of human norovirus GII.4 VP1 leads to assembly of T=4 virus-like particles

Human noroviruses are a leading cause of acute gastroenteritis, yet there are still no vaccines or antivirals available. Expression of the norovirus capsid protein (VP1) in insect cells typically results in the formation of virus-like particles (VLPs) that are morphologically and antigenically comparable to native virions. Indeed, several different norovirus VLP candidates are currently used in clinical trials. So far, structural analysis of norovirus VLPs showed that the capsid has a T = 3 icosahedral symmetry and is composed of 180 copies of VP1 that are folded into three quasi-equivalent subunits (A, B, and C). In this study, the VLP structures of two norovirus GII.4 genetic variants that were identified in 1974 and 2012 were determined using cryo-EM. Surprisingly, we found that greater than 95% of these GII.4 VLPs were larger than virions and 3D reconstruction showed that these VLPs exhibited T = 4 icosahedral symmetry. We also discovered that the T = 4 VLPs presented several novel structural features. The T = 4 particles assembled from 240 copies of VP1 that adopted four quasi-equivalent conformations (A, B, C, and D) and formed two distinct dimers, A/B and C/D. The protruding domains were elevated ∼21 Å off the capsid shell, which was ∼7 Å more than in the previously studied GII.10 T = 3 VLPs. A small cavity and flap-like structure at the icosahedral two-fold axis disrupted the contiguous T = 4 shell. Overall, our findings indicated that GII.4 VP1 sequences assemble into T = 4 VLPs and these larger particles might have important consequences for VLP-based vaccine development.

Crystal structures and Hirshfeld surface analyses of 4,4'-{[1,3-phenyl-enebis(methyl-ene)]bis-(-oxy)}bis-(3-meth-oxy-benzaldehyde) and 4,4'-{[(1,4-phenyl-ene-bis(methyl-ene)]bis-(-oxy)}bis-(3-meth-oxy-benzalde-hyde).

The title compounds, C24H22O6 (I) and C24H22O6 (II), each crystallize with half a mol-ecule in the asymmetric unit. The whole mol-ecule of compound (I) is generated by twofold rotation symmetry, the twofold axis bis-ecting the central benzene ring. The whole mol-ecule of compound (II) is generated by inversion symmetry, the central benzene ring being located on an inversion center. In (I), the outer benzene rings are inclined to each other by 59.96 (10)° and by 36.74 (9)° to the central benzene ring. The corresponding dihedral angles in (II) are 0.0 and 89.87 (12)°. In the crystal of (I), mol-ecules are linked by C-H⋯O hydrogen bonds and C-H⋯π inter-actions, forming ribbons propagating along the [10] direction. In the crystal of (II), mol-ecules are linked by C-H⋯O hydrogen bonds, forming a supra-molecular framework. The Hirshfeld surface analyses indicate that for both compounds the H⋯H contacts are the most significant, followed by O⋯H/H⋯O and C⋯H/H⋯C contacts.

Purely rotational symmetry-protected topological crystalline insulator -Bi4Br4

Rotational-symmetry-protected topological crystalline insulators (TCIs) are expected to host unique boundary modes, in that the surface normal to the rotational axis can feature surface states with ‘unpinned’ Dirac points, which are not constrained to lie on high symmetry points or lines, but can lie at any general k point in the Brillouin zone. Also, as a higher order bulk boundary correspondence is involved here, a three-dimensional (3D) TCI can support one-dimensional (1D) helical edge states. Using first-principles band structure calculations, we identify the van der Waals material -Bi4Br4 as a purely rotation symmetry protected TCI. We show that the surface of Bi4Br4 exhibits a pair of unpinned topological Dirac fermions which are related to the presence of a two-fold rotation axis. These unpinned Dirac fermions possess an exotic spin texture which will be highly favorable for spin transport, and a band structure that consists of van Hove singularities due to a Lifshitz transition. We also identify 1D topological hinge states along the edges of an -Bi4Br4 rod. We comment on how the predicted topological features in -Bi4Br4 could be accessed experimentally.

Crystal structure and DFT study of (E)-2-chloro-4-{[2-(2,4-di-nitro-phen-yl)hydrazin-1-yl-idene]meth-yl}phenol aceto-nitrile hemisolvate.

The title Schiff base compound, C13H9ClN4O5·0.5CH3CN, crystallizes as an aceto-nitrile hemisolvate; the solvent mol-ecule being located on a twofold rotation axis. The mol-ecule is nearly planar, with a dihedral angle between the two benzene rings of 3.7 (2)°. The configuration about the C=N bond is E, and there is an intra-molecular N-H⋯Onitro hydrogen bond present forming an S(6) ring motif. In the crystal, mol-ecules are linked by O-H⋯O and N-H⋯O hydrogen bonds, forming layers lying parallel to (10). The layers are linked by C-H⋯Cl hydrogen bonds, forming a supra-molecular framework. Within the framework there are offset π-π stacking inter-actions [inter-centroid distance = 3.833 (2) Å] present involving inversion-related mol-ecules. The DFT study shows that the HOMO and LUMO are localized in the plane extending from the phenol ring to the 2,4-di-nitro-benzene ring, and the HOMO-LUMO gap is found to be 0.13061 a.u.

Crystal structure of bis-(4-meth-oxy-pyridine-κN)(meso-5,10,15,20-tetra-phenyl-porphyrinato-κ4 N,N',N'',N''')iron(III) perchlorate.

In the crystal structure of the title compound, [Fe(C44H28N4)(C6H7NO)2]ClO4, the FeIII ions are coordinated in an octa-hedral fashion by four N atoms of the porphyrin moiety and two N atoms of two 4-meth-oxy-pyridine ligands into discrete complexes that are located on inversion centers. Charge-balance is achieved by perchlorate anions that are disordered around twofold rotation axes. In the crystal structure, the discrete cationic complexes and the perchlorate anions are arranged into layers with weak C-H⋯O inter-actions between the cations and the anions. The porphyrin moieties of neighboring layers show a herringbone-like arrangement.

The crystal structures and Hirshfeld surface analysis of N',N'''-((1E,1'E)-{[methyl-enebis(-oxy)]bis-(6-bromo-3,1-phenyl-ene)}bis-(methan-ylyl-idene))bis-(isonicotinohydrazide) dihydrate and N',N'''-((1E,1'E)-{[butane-1,4-diylbis(-oxy)]bis-(2,1-phenyl-ene)}bis-(methan-ylyl-idene))bis-(isonicotino-hydrazide) [+ solvent

The title compounds, C27H20Br2N6O4·2H2O, (I), and C30H28N6O4·[+ solvent], (II), both crystallize with one half-mol-ecule in the asymmetric unit. The whole mol-ecule of (I) is generated by twofold rotation symmetry, with the twofold rotation axis bis-ecting the C atom of the -O-CH2-O- bridge. This results in a folded or U-shaped conformation of the mol-ecule. The whole mol-ecule of (II) is generated by inversion symmetry, with the central CH2-CH2 bond of the -O-(CH2)4-O- bridge being located about a center of inversion. This results in a step-like conformation of the mol-ecule. The central C(=O)N-N=C regions of the isonicotinohydrazide moieties in both compounds are planar and the configuration about the imine C=N bonds is E. In compound (I), the benzene and pyridine rings are inclined to each other by 37.60 (6)°. The two symmetry-related pyridine rings are inclined to each other by 74.24 (6)°, and the two symmetry-related benzene rings by 7.69 (6)°. In compound (II), the benzene and pyridine rings are inclined to each other by 25.56 (11)°. The symmetry-related pyridine rings are parallel, as are the two symmetry-related benzene rings. In the crystal of (I), a pair of water mol-ecules link the organic mol-ecules via Owater-H⋯O and Owater-H⋯N hydrogen bonds, forming chains along [001], and enclosing an R 4 2(8) and two R 1 2(5) ring motifs. The chains are linked by N-H⋯Npyridine hydrogen bonds, forming a supra-molecular framework. There are also a number of C-H⋯O hydrogen bonds, and C-H⋯π and offset π-π inter-actions [inter-planar distance = 3.294 (1) Å] present reinforcing the framework. In the crystal of (II), mol-ecules are linked by N-H⋯Npyridine hydrogen bonds, forming a supra-molecular framework. Here too there are also a number of C-H⋯O hydrogen bonds present, and a C-H⋯π inter-action, reinforcing the framework. For compound (II), a region of disordered electron density was corrected for using the SQUEEZE [Spek (2015 ▸). Acta Cryst. C71, 9-18] routine in PLATON. Their formula mass and unit-cell characteristics were not taken into account during refinement.

1,3-Bis(2-cyanopropan-2-yl)-5-methylbenzene

The complete molecule of the title compound [systematic name: 2,2′-(5-methyl-1,3-phenylene)bis(2-methylpropanenitrile)] is generated by a crystallographic twofold axis, which leads to disorder of the H atoms on the methyl group attached to the benzene ring. The dihedral angle between the benzene ring and the nitrile group is 26.2 (2)°. In the crystal, pairs of weak C—H...π interactions link molecules into dimers. The molecule absorbs at 212 nm as a result of a π–π* transition.

The third structural switch in the archaeal translation initiation factor 2 (aIF2) molecule and its possible role in the initiation of GTP hydrolysis and the removal of aIF2 from the ribosome.

The structure of the γ subunit of archaeal translation initiation factor 2 (aIF2) from Sulfolobus solfataricus (SsoIF2γ) was determined in complex with GDPCP (a GTP analog). Crystals were obtained in the absence of magnesium ions in the crystallization solution. They belonged to space group P1, with five molecules in the unit cell. Four of these molecules are related in pairs by a common noncrystallographic twofold symmetry axis, while the fifth has no symmetry equivalent. Analysis of the structure and its comparison with other known aIF2 γ-subunit structures in the GTP-bound state show that (i) the magnesium ion is necessary for the formation and the maintenance of the active form of SsoIF2γ and (ii) in addition to the two previously known structural switches 1 and 2, eukaryotic translation initiation factor 2 (eIF2) and aIF2 molecules have another flexible region (switch 3), the function of which may consist of initiation of the hydrolysis of GTP and the removal of e/aIF2 from the ribosome after codon-anticodon recognition.

The structure of an iron-containing alcohol dehydrogenase from a hyperthermophilic archaeon in two chemical states.

An iron-containing alcohol dehydrogenase (FeADH) from the hyperthermophilic archaeon Thermococcus thioreducens was crystallized in unit cells belonging to space groups P21, P212121 and P43212, and the crystal structures were solved at 2.4, 2.1 and 1.9 Å resolution, respectively, by molecular replacement using the FeADH from Thermotoga maritima (Schwarzenbacher et al., 2004) as a model. In the monoclinic and orthorhombic crystals the dehydrogenase (molecular mass 41.5 kDa) existed as a dimer containing a twofold noncrystallographic symmetry axis, which was crystallographic in the tetragonal crystals. In the monoclinic and orthorhombic asymmetric units one molecule contained iron and an NADP molecule, while the other did not. The tetragonal crystals lacked both iron and NADP. The structure is very similar to that of the FeADH from T. maritima (average r.m.s. difference for Cα atoms of 1.8 Å for 341 aligned atoms). The iron, which is internally sequestered, is bound entirely by amino acids from one domain: three histidines and one aspartic acid. The coenzyme is in an extended conformation, a feature that is common to the large superfamily of NADH-dependent dehydrogenases that share a classical nucleotide-binding domain. A long broad tunnel passes entirely through the enzyme between the two domains, completely encapsulating the coenzyme.

Synthesis, DFT analysis and DNA studies, cytotoxicity and luminescence properties of a dinuclear copper(II) complex with 1,10-phenanthroline and 4-aminobenzoate

The dinuclear copper(II) complex, [Cu2(phen)2(4-aminobenzoate)2(H2O)2](NO3)2·2(4-aminobenzoic acid)·3H2O (phen = 1,10-phenanthroline), has been synthesized and structurally characterized by elemental analyses, IR, EPR, UV-visible and single-crystal X-ray crystallography. The complex crystallized in a monoclinic system with space group C2/c, a = 26.0022(10) Å, b = 10.2524(4) Å, c = 20.9983(7) Å, α = 90°, β = 106.9550(10)° and γ = 90°. The Cu(II) ion adopts a distorted square-pyramidal geometry formed by two N atoms from the phen ligand and two O atoms of the two 4-aminobenzoic acid ligands and one water O atom. The Cu…Cu separation is 3.0570(5) Å. A twofold axis passes through the midpoint of the Cu-Cu vector. The complex has intraligand (π–π*) fluorescence properties. The binding of this dinuclear copper(II) complex with calf thymus DNA (CT-DNA) was investigated by UV-vis absorption, fluorescence spectroscopic, cyclic voltammetric and viscosity techniques. Also, the cleavage of pBR322 DNA with dinuclear copper(II) complex was studied using gel electrophoresis method. The exhibited potent cytotoxic effects against human cell line (HepG2) and it was found to have good antimicrobial activities. The primary coordination sphere of dinuclear copper(II) complex is optimized, structural parameters are calculated and energy gaps of frontier orbital (HOMO-LUMO) have been calculated with B3LYP/6-31G/LANL2DZ level of theory in the gaseous phase. The calculated geometric and spectral results reproduced the experimental data with well agreement. Theoretical calculated molecular orbitals (HOMO-LUMO) and their energies have been calculated that suggest charge transfer occurs within the complex.

Formation and crystallographic orientation study of quasicrystal, 2/1 and 1/1 approximants in Cd–Mg–Y system using electron backscatter diffraction (EBSD)

ABSTRACT A partial isothermal ternary phase diagram of the Cd–Mg–Y system including icosahedral quasicrystal (i-QC) and 1/1 approximant (APP) was obtained at 673 K. The stability of the i-QC and APPs in terms of composition and temperature was studied, as a result of which the 2/1 APP phase was discovered at 773 K. Moreover, the i-QC phase was found to be stable at lower Y concentrations of ∼12–13 at.%, as compared to the 1/1 APP, which showed ∼15–16 at.% Y. Single i-QC, 2/1 and 1/1 APP grains were also synthesized applying centrifuging system. Electron backscatter diffraction (EBSD) characterization of the obtained i-QC and APPs revealed almost the same Kikuchi patterns for the i-QC and 2/1 APP, indicating high resemblance of their structures. However, the Kikuchi pattern acquired from the 1/1 APP was distinguishable from the one obtained from the i-QC as it showed split bands. The occurrence of the split bands was associated with significant deviation from a perfect icosahedral symmetry. This was also confirmed by analysing calculated electron diffraction and Kikuchi patterns along pseudo-five-fold axes of the 2/1 and 1/1 APPs. Finally, orientation relationships between the i-QC, 1/1 APP and α-Mg were investigated by analysing acquired EBSD Kikuchi patterns from the respective domains. Accordingly, three perpendicular two-fold axes of the i-QC and {100} axes of the 1/1 APP occur along three mutually orthogonal {0001}, {10-10} and {11-20} axes of the α-Mg.

Synthesis, Crystal Structure, and Magnetic Property of four Manganese(II) Complexes with Bulky Schiff bases Derived from Amantadine and Rimantadine

The reactions of manganese(II) chloride tetrahydrate and four bulky Schiff base ligands derived from amantadine (or rimantadine) and salicylaldehyde (or 4-methoxysalicylaldehyde) generated four novel complexes, C34H42Cl2MnN2O2 (I), C36H46Cl2MnN2O4 (II), C38H50Cl2MnN2O2 (III), and C40H54Cl2MnN2O4 (IV), respectively. These complexes were characterized by melting point, infrared spectra, elemental analysis, magnetic susceptibility, molar conductance and single-crystal X-ray diffraction (CIF files CCDC nos. 1 540 253 (I), 1 540 254 (II), 1 540 255 (III), 1 540 256 (IV)). Single-crystal X-ray diffraction analysis reveals that I, III and IV crystallize in the orthorhombic system with space groups P212121, Pbcn and Pcan, respectively, whereas II crystallizes in the monoclinic system with space group P21/n. Each asymmetric unit for I–IV consists of one manganese(II) atom, two Schiff base ligands and two chlorine atoms. The central manganese(II) atoms lie on a twofold rotation axis in III and IV, whereas manganese(II) atoms lie on general positions in I and II. In these complexes molecules, manganese(II) atoms is four-coordinated via two chlorine atoms and two oxygen atoms from the corresponding Schiff base ligands, forming a distorted tetrahedral geometry.